The MT4 platform also doesn't adjust when I changed font settings in OS Windows 8.1

You must reboot the PC after lowering the resolution in order for MT4 to detect the lower resolution. After the reboot, you will have the same look and font sizes in MT4 as if you had a non-4K monitor.

If you just change the resolution to, say, 1920 x 1080, without rebooting, MT4 still thinks you are in 4K mode and will show the tiny fonts, even though the Windows desktop has changed to the lower resolution.

Eventually MT4 will need to support 4K displays, but this seems to be the best solution for now.